1. Field of the Invention (Technical Field)
The present invention relates to long-wavelength infra-red (IR) night vision goggles.
2. Description of Related Art
Current night vision devices are image intensification apparatuses that amplify the ambient visible light illumination view by a factor of 10 or more. As used in aircraft or other military applications, these devices usually take the form of goggles worn by the pilot. Night vision devices usually include a photocathode 12 that converts photons to electrons, a multiplier 14, and a phosphor screen 16 to convert electrons back into photons (FIGS. 1 and 2). Accordingly, typical night vision devices (or image intensifiers) only work with visible wavelengths of radiation. This type of prior art device is discussed in detail in Bentham NVIS Compatibility (A Primer), Issue 2.01, Bentham Instruments Ltd. (February 1997).
Other existing devices image infrared (IR)/thermal radiation from objects in the dark. A typical device used is a charge coupled device (CCD) sensor that is sensitive in the IR.
A fused system (e.g., U.S. Pat. Nos. 4,751,571 and 5,035,472) has been used that combines both intensified visible and IR radiation. However, the IR radiation of such a system is confined only to the near IR region optimized to detect objects at very high temperatures of about 1000 degrees celsius. For temperatures of objects near room-temperature, maximum IR emission occurs within the “far-IR” region of 7 to 14 microns.
The present invention provides night vision goggles operating in the long wavelength IR region by employing an uncooled IR focal plane array (IRFPA).